This invention relates to combustors for gas turbine engines and in particular to wall elements for use in wall structures of combustors of gas turbine engines.
It is known to construct combustors of gas turbine engines with an outer wall and an inner wall, the inner wall being formed of a plurality of tiles. Cooling air is used to prevent overheating of the combustor walls, but air pollution regulations require a high proportion of air to be used for combustion so that the air available for cooling is reduced. Known tiles give rise to problems because of the conflicting requirements of cooling and emission reduction.
According to one aspect of this invention, there is provided a wall element for a wall structure of a gas turbine engine combustor, the wall element comprising a base portion having an axis which, in use extends generally parallel to the principal axis of the engine, wherein the dimension of said base portion parallel to said axis thereof is greater than substantially 20% of the dimension of the base portion transverse to said axis, and the base portion includes a plurality of rows of mixing ports to allow gas to enter the combustor in use.
The dimension of said base portion parallel to said axis thereof may be greater than substantially 40% of its length transverse to said axis. In one embodiment, the dimension of the base portion parallel to said axis is substantially equal to its dimension transverse to said axis thereof.
Desirably, the dimension of the wall element parallel to said axis thereof is greater than substantially 40 mm. Said dimension may be between substantially 40 mm and substantially 80 mm, but, preferably, the dimension of the wall element parallel to said axis thereof is greater than substantially 80 mm. In one embodiment, the dimension of the wall element parallel to said axis thereof is substantially 250 mm and may be the same as said dimension of the wall element transverse to said axis thereof.
In one embodiment, the wall element has two of said rows. Preferably, each row extends substantially transverse to said axis of the wall element.
The base portion may define a plurality of apertures for the passage of a cooling fluid to cool a surface of the wall element which, in use, faces, inwardly of the combustor. Preferably the apertures are in the form of effusion holes and may be arranged to direct a film of cooling air along said surface of the base portion.
The apertures may be defined at or adjacent the edge regions of the base portion. The base portion may be provided with upstream and downstream edge regions, the apertures preferably being located adjacent the downstream edge region.
Alternatively, or in addition, the apertures may be spaced from the edge regions, and are preferably spaced along a line extending substantially transverse to said axis of the wall structure. Conveniently, said line of apertures extends substantially centrally of the base portion. Preferably, the apertures are angled to direct the cooling fluid towards the downstream edge of the base portion.
At least the downstream edge of the base portion may be provided with an outwardly directed flange which, in use, engages an outer wall of the combustor. The outwardly directed flange may include a lip portion adapted to engage an adjacent downstream wall element. An outwardly directed flange may be provided on the upstream edge of the base portion.
Alternatively, downstream edge of the base portion may be open to allow cooling fluid to flow over said downstream edge. The upstream edge may be open to allow cooling fluid to flow over the upstream edge.
The wall element may be stepped to correspond with a step on the outer wall of the combustor.
In one embodiment, the wall element includes a barrier member extending at least part way across the base portion, the barrier member being provided to control the flow of cooling fluid across said base portion.
Preferably, the barrier member is provided on the wall element such that cooling fluid passing over the base portion on one side of the barrier member is directed away from the barrier member on said one side.
In one embodiment, the barrier member may be provided such that cooling fluid passing over the base portion on first and second opposite sides of the barrier member is directed in first and second opposite directions away from said barrier member.
Preferably, the barrier member acts such that cooling fluid passing over the base portion on one side thereof is prevented from passing over the barrier member to the other side. Preferably, the first and second sides of the barrier member are isolated from each other.
Preferably, the barrier member extends transverse to said axis of the wall structure. The barrier member preferably extends substantially perpendicular to said axis of the wall structure. In another embodiment, the barrier member extends substantially parallel to said axis of the wall structure.
The barrier member may extend substantially wholly across the base portion.
The wall element may be provided with a plurality of barrier members which may define a boundary of a region for the flow of a cooling fluid, wherein said region is isolated from the remainder of the wall element, thereby resulting in increased or decreased pressure of said cooling fluid in said region relative to the remainder of said wall element.
The plurality of barrier members may each be axially extending barrier members or may each be transversely extending barrier members.
Preferably, said plurality of barrier members comprise at least one axially extending barrier member and at least one transversely extending barrier member. Each of the plurality of barrier members may engage or abut each adjacent barrier member to define said region.
The, or each, barrier member may be in the form of an elongate bar which may extend substantially from said base portion to said outer wall.
The inner wall may comprise a plurality of said wall elements.
According to another aspect of this invention, there is provided a wall element for a combustor of a gas turbine engine, the wall element comprising a base portion having an axis which, in use, extends generally parallel to the principal axis of the engine, and the base portion having a first pair of opposite edges extending transverse to said axis of the wall element and a second pair of opposite edges extending transverse to said first pair wherein at least one of said second pair of edges is angled relative to said axis of the base portion to extend obliquely to said axis.
Preferably, both of the edges of said second pair are angled relative to the axis of the base portion. Conveniently, both edges of said second pair extend substantially parallel to each other.
The or each edge of said second pair may be angled relative to the axis of the base portion at an angle of between substantially 10xc2x0 and substantially 40xc2x0, preferably substantially 20xc2x0 and substantially 30xc2x0. More preferably, the angle is substantially 30xc2x0.
In one embodiment, the wall element comprises the features of the wall element described in paragraphs three to twenty three above.
According to another aspect of this invention, there is provided a combustor wall structure of a gas turbine engine, the wall structure comprising inner and outer walls, the inner wall including at least one wall element as described above.
Embodiments of the invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings, in which: